Our "database" is actually a collection of single tenant databases (meaning you do not share a database with anyone else). It is stored in Amazon's Relational Database System or RDS. We use RDS Automated Backups which is set to take a snapshot of the entire collection of databases each night for the last 7 days. This is used for disaster recovery in case we need to restore every single database.
Additionally, we take individual database backups so that we may quickly restore a single database. These are stored in Amazon's secure cloud file storage service, S3. We retain daily backups for 30 days, weekly backups for 90 days and monthly backups indefinitely.
The RDS database instance and its backups are contained in a Virtual Private Cloud, or VPC, which is isolated from public access via a strict firewall rule set. The Amazon S3 instance that houses the individual database backups is also under strict provisioning, only allowing access to our data services team for database recovery.
All of the above backups are retained off-site, in the cloud, using Amazon Web Services and their secure data centers.